This invention relates to a hydraulic push drive for a pusher centrifuge, with a piston and a piston rod located in a rotating piston body. The present invention is concerned, more particularly, with such a hydraulic drive which is designed to permit during operation controlling of stroke length and stroke center, even at high switching rates and/or high stroke frequencies.
In larger machines, push drives for pusher centrifuges operate by a direct hydraulic principle, i.e., by means of alternate pressure application to a piston rotating with the basket of the centrifuge. The problems associated with this type of drive involve the reversal of the pressure application at the end of the stroke; with a stop-actuated reversing valve in the piston body, a simple solution is available, but one in which the stroke length cannot be adjusted during operation and which must be rejected in view of the fact that adjustments of stroke length and stroke center are required by chemical engineering considerations.
Makeshift solutions involving electronic scanning of the stroke movement and operation of electrohydraulic valves have been proposed, but are sharply limited in application by the switching rate of the valves.